6,475 research outputs found
Stressful life events are associated with low secretion rates of immunoglobulin A in saliva in the middle aged and elderly
Whether chronic stress experience is related to down-regulation of secretory immunoglobulin A (S-IgA) was tested in two substantial cohorts, one middle-aged (N = 640) and one elderly (N = 582), comprising similar numbers of men (N = 556) and women (N = 666) and manual (N = 606) and non-manual (N = 602) workers. Participants indicated from a list of major stressful life events up to six they had experienced in the previous two years. They also rated how disruptive and stressful the events were, at the time and now, as well as their perceived seriousness; the products of these impact values and event frequency were adopted as measures of stress load. From unstimulated 2-minute saliva samples, saliva volume and S-IgA concentration were measured, and S-IgA secretion rate determined as their product. There was a negative association between the stress load measures and S-IgA secretion rate, still evident following adjustment for such variables as smoking and saliva volume. The associations also withstood adjustment for sex, cohort, and household occupational status. Although these associations are small in terms of the amount of variance explained, they nonetheless suggest that chronic stress experience either decreases IgA production by the local plasma cells or reduces the efficiency with which S-IgA is transported from the glandular interstitium into saliva. Given the importance of S-IgA in immune defence at mucosal surfaces and the frequency with which infections are initiated at these surfaces, S-IgA down-regulation could be a means by which chronic stress increases susceptibility to upper respiratory tract infection
Operator product expansion for B-meson distribution amplitude and dimension-5 HQET operators
When the bilocal heavy-quark effective theory (HQET) operator for the B-meson
distribution amplitude has a light-like distance t between the quark and
antiquark fields, the scale \sim 1/t separates the UV and IR regions, which
induce the cusp singularity in radiative corrections and the mixing of
multiparticle states in nonperturbative corrections, respectively. We treat
these notorious UV and IR behaviors simultaneously using the operator product
expansion, with the local operators of dimension and radiative
corrections at order \alpha_s for the corresponding Wilson coefficients. The
result is derived in the coordinate space, which manifests the Wilson
coefficients with Sudakov-type double logarithms and the higher-dimensional
operators with additional gluons. This result yields the B-meson distribution
amplitude for t less than \sim 1 GeV^{-1}, in terms of and the two additional HQET parameters as matrix elements of dimension-5
operators. The impact of these novel HQET parameters on the integral relevant
to exclusive B decays, \lambda_B, is also discussed.Comment: 13 pages, 2 figures; minor corrections, version published in PL
Galaxy Groups in the SDSS DR4: I. The Catalogue and Basic Properties
We use a modified version of the halo-based group finder developed by Yang et
al. to select galaxy groups from the Sloan Digital Sky Survey (SDSS DR4). In
the first step, a combination of two methods is used to identify the centers of
potential groups and to estimate their characteristic luminosity. Using an
iterative approach, the adaptive group finder then uses the average
mass-to-light ratios of groups, obtained from the previous iteration, to assign
a tentative mass to each group. This mass is then used to estimate the size and
velocity dispersion of the underlying halo that hosts the group, which in turn
is used to determine group membership in redshift space. Finally, each
individual group is assigned two different halo masses: one based on its
characteristic luminosity, and the other based on its characteristic stellar
mass. Applying the group finder to the SDSS DR4, we obtain 301237 groups in a
broad dynamic range, including systems of isolated galaxies. We use detailed
mock galaxy catalogues constructed for the SDSS DR4 to test the performance of
our group finder in terms of completeness of true members, contamination by
interlopers, and accuracy of the assigned masses. This paper is the first in a
series and focuses on the selection procedure, tests of the reliability of the
group finder, and the basic properties of the group catalogue (e.g. the
mass-to-light ratios, the halo mass to stellar mass ratios, etc.). The group
catalogues including the membership of the groups are available at
http://gax.shao.ac.cn/data/Group.html and
http://www.astro.umass.edu/~xhyang/Group.htmlComment: 19 pages, 12 figures, Accepted for publication in ApJ. Group
catalogues are available at http://gax.shao.ac.cn/data/Group.html and
http://www.astro.umass.edu/~xhyang/Group.htm
The Alignment between Satellites and Central Galaxies: Theory vs. Observations
Recent studies have shown that the distribution of satellite galaxies is
preferentially aligned with the major axis of their central galaxy. The
strength of this alignment has been found to depend strongly on the colours of
the satellite and central galaxies, and only weakly on the mass of the halo in
which the galaxies reside. In this paper we study whether these alignment
signals, and their dependence on galaxy and halo properties, can be reproduced
in a hierarchical structure formation model of a CDM concordance
cosmology. To that extent we use a large -body simulation which we populate
with galaxies following a semi-analytical model for galaxy formation. We find
that if the orientation of the central galaxy is perfectly aligned with that of
its dark matter halo, then the predicted central-satellite alignment signal is
much stronger than observed. If, however, the minor axis of a central galaxy is
perfectly aligned with the angular momentum vector of its dark matter halo, we
can accurately reproduce the observed alignment strength as function of halo
mass and galaxy color. Although this suggests that the orientation of central
galaxies is governed by the angular momentum of their dark matter haloes, we
emphasize that any other scenario in which the minor axes of central galaxy and
halo are misaligned by (on average) will match the data
equally well. Finally, we show that dependence of the alignment strength on the
color of the central galaxy is most likely an artefact due to interlopers in
the group catalogue. The dependence on the color of the satellite galaxies, on
the other hand, is real and owes to the fact that red satellites are associated
with subhaloes that were more massive at their time of accretion.Comment: 13 Pages, 10 Figures, one figure replaced. added in discussion about
comparison with others results, Updated version to match accepted version to
MNRA
Constraining the Star Formation Histories in Dark Matter Halos: I. Central Galaxies
Using the self-consistent modeling of the conditional stellar mass functions
across cosmic time by Yang et al. (2012), we make model predictions for the
star formation histories (SFHs) of {\it central} galaxies in halos of different
masses. The model requires the following two key ingredients: (i) mass assembly
histories of central and satellite galaxies, and (ii) local observational
constraints of the star formation rates of central galaxies as function of halo
mass. We obtain a universal fitting formula that describes the (median) SFH of
central galaxies as function of halo mass, galaxy stellar mass and redshift. We
use this model to make predictions for various aspects of the star formation
rates of central galaxies across cosmic time. Our main findings are the
following. (1) The specific star formation rate (SSFR) at high increases
rapidly with increasing redshift [] for halos of a given
mass and only slowly with halo mass () at a given , in
almost perfect agreement with the specific mass accretion rate of dark matter
halos. (2) The ratio between the star formation rate (SFR) in the main-branch
progenitor and the final stellar mass of a galaxy peaks roughly at a constant
value, , independent of halo mass or the
final stellar mass of the galaxy. However, the redshift at which the SFR peaks
increases rapidly with halo mass. (3) More than half of the stars in the
present-day Universe were formed in halos with 10^{11.1}\msunh < M_h <
10^{12.3}\msunh in the redshift range . (4) ... [abridged]Comment: 15 figures, 22 pages, Accepted for publication in Ap
A ground system for early forest fire detection based on infrared signal processing
This article presents a ground remote automatic system for forest surveillance based on infrared signal processing applied to early fire detection. Advanced techniques, which are based on infrared signal processing, are used in order to process the captured images. With the aim of determining the presence or absence of fire, the system performs the fusion of different detectors that exploit different expected characteristics of a real fire, such as persistence and increase. Theoretical simulations and practical results are presented to corroborate the control of the probability of false alarm. Results in a real environment are also presented to authenticate the accuracy of the operation of the proposed system. In particular, some experiments have been done to evaluate the delay of the system (tens of seconds on average) in detecting a controlled ground fire in a range of 1-10 km. Moreover, temporary evolution of false alarms and true detections are presented to evaluate the long-term performance of the system in a real environment. We have reached a detection probability of 100% at a false alarm rate of around 1 x 10(-9).This work has been supported by Generalitat Valenciana, under grant GVEMP06/001, and by MEC under the FPU programme.Bosch Roig, I.; Gómez, S.; Vergara Domínguez, L. (2011). A ground system for early forest fire detection based on infrared signal processing. International Journal of Remote Sensing. 32(17):4857-4870. https://doi.org/10.1080/01431161.2010.490245S485748703217Arrue, B. C., Ollero, A., & Matinez de Dios, J. R. (2000). An intelligent system for false alarm reduction in infrared forest-fire detection. IEEE Intelligent Systems, 15(3), 64-73. doi:10.1109/5254.846287Bernabeu, P., Vergara, L., Bosh, I., & Igual, J. (2004). A prediction/detection scheme for automatic forest fire surveillance. Digital Signal Processing, 14(5), 481-507. doi:10.1016/j.dsp.2004.06.003Briz, S. (2003). Reduction of false alarm rate in automatic forest fire infrared surveillance systems. Remote Sensing of Environment, 86(1), 19-29. doi:10.1016/s0034-4257(03)00064-6Pastor, E. (2003). Mathematical models and calculation systems for the study of wildland fire behaviour. Progress in Energy and Combustion Science, 29(2), 139-153. doi:10.1016/s0360-1285(03)00017-0Vergara, L., & Bernabeu, P. (2000). Automatic signal detection applied to fire control by infrared digital signal processing. Signal Processing, 80(4), 659-669. doi:10.1016/s0165-1684(99)00159-0Vergara, L., & Bernabeu, P. (2001). Simple approach to nonlinear prediction. Electronics Letters, 37(14), 926. doi:10.1049/el:20010616Vicente, J., & Guillemant, P. (2002). An image processing technique for automatically detecting forest fire. International Journal of Thermal Sciences, 41(12), 1113-1120. doi:10.1016/s1290-0729(02)01397-
Magetoresistance of RuO_2-based resistance thermometers below 0.3 K
We have determined the magnetoresistance of RuO_2-based resistors (Scientific
Instruments RO-600) between 0.05 K and 0.3 K in magnetic fields up to 8 T. The
magnetoresistance is negative around 0.5 T and then becomes positive at larger
fields. The magnitude of the negative magnetoresistance increases rapidly as
the temperature is lowered, while that of the positive magnetoresistance has
smaller temperature dependence. We have also examined the temperature
dependence of the resistance below 50 mK in zero magnetic field. It is
described in the context of variable-range-hopping conduction down to 15 mK.
Hence, the resistors can be used as thermometers down to at least 15 mK.Comment: 6 pages with 7 embedded figures. Published version (very minor
changes
Can a Funny Chatbot Make a Difference? Infusing Humor into Conversational Agent for Behavioral Intervention
Regular physical activity is crucial for reducing the risk of
non-communicable disease (NCD). With NCDs on the rise globally, there is an
urgent need for effective health interventions, with chatbots emerging as a
viable and cost-effective option because of limited healthcare accessibility.
Although health professionals often utilize behavior change techniques (BCTs)
to boost physical activity levels and enhance client engagement and motivation
by affiliative humor, the efficacy of humor in chatbot-delivered interventions
is not well-understood. This study conducted a randomized controlled trial to
examine the impact of the generative humorous communication style in a 10-day
chatbot-delivered intervention for physical activity. It further investigated
if user engagement and motivation act as mediators between the communication
style and changes in physical activity levels. 66 participants engaged with the
chatbots across three groups (humorous, non-humorous, and no-intervention) and
responded to daily ecological momentary assessment questionnaires assessing
engagement, motivation, and physical activity levels. Multilevel time series
analyses revealed that an affiliative humorous communication style positively
impacted physical activity levels over time, with user engagement acting as a
mediator in this relationship, whereas motivation did not. These findings
clarify the role of humorous communication style in chatbot-delivered physical
activity interventions, offering valuable insights for future development of
intelligent conversational agents incorporating humor
The cross-correlation between galaxies of different luminosities and Colors
We study the cross-correlation between galaxies of different luminosities and
colors, using a sample selected from the SDSS Dr 4. Galaxies are divided into 6
samples according to luminosity, and each of these samples is divided into red
and blue subsamples. Projected auto-correlation and cross-correlation is
estimated for these subsample. At projected separations r_p > 1\mpch, all
correlation functions are roughly parallel, although the correlation amplitude
depends systematically on luminosity and color. On r_p < 1\mpch, the auto- and
cross-correlation functions of red galaxies are significantly enhanced relative
to the corresponding power laws obtained on larger scales. Such enhancement is
absent for blue galaxies and in the cross-correlation between red and blue
galaxies. We esimate the relative bias factor on scales r > 1\mpch for each
subsample using its auto-correlation function and cross-correlation functions.
The relative bias factors obtained from different methods are similar. For blue
galaxies the luminosity-dependence of the relative bias is strong over the
luminosity range probed (-23.0<M_r < -18.0),but for red galaxies the dependence
is weaker and becomes insignificant for luminosities below L^*. To examine
whether a significant stochastic/nonlinear component exists in the bias
relation, we study the ratio R_ij= W_{ii}W_{jj}/W_{ij}^2, where W_{ij} is the
projected correlation between subsample i and j. We find that the values of
R_ij are all consistent with 1 for all-all, red-red and blue-blue samples,
however significantly larger than 1 for red-blue samples. For faint red - faint
blue samples the values of R_{ij} are as high as ~ 2 on small scales r_p < 1
\mpch and decrease with increasing r_p.Comment: 25 pages, 18 figures, Accepted for publication in Ap
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